• Journal of Aerospace System Engineering
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• v.8 no.1
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• pp.30-35
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• 2014

This study has been conducted to develop an ejector system applied in the aircraft engine-bay ventilation system. Tandem-Ejector was selected as a component of ventilation system because it could achieve high ventilation performance in spite of motive flow with small flow rate. Tandem-Ejector is composed of a primary nozzle and two mixing ducts ($1^{st}$ mixing duct and $2^{nd}$ mixing duct). In this study, 1-D Tandem-Ejector model has been built with conservation laws and isentropic relation for 1-D ejector sizing and performance prediction. Computational Fluid Dynamics(CFD) has been conducted to investigate ejector performance and flow characteristics in the ejector. Also, Tandem-Ejector performance tests have been conducted to obtain ejector pumping performance and to investigate stand-off (gap between primary nozzle and $1^{st}$ mixing duct inlet) effect on ejector pumping performance.

• Journal of Korean Society of Water and Wastewater
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• v.33 no.6
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• pp.447-456
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• 2019

This study focused on natural organic matter and trihalomethane removal by ozonation with various ferrous concentration in surface water. Ozonation is more affected by injection concentration than reaction time. dissolved organic carbon removal rates in ozonation increased with the increase in ferrous concentration. The highest removal was obtained at 6 mg/L of ferrous concentration. When 1 mg/L of ferrous was added with 2 mg/L of ozone concentration, it was found to be a rapid decrease in specific ultraviolet absorbance at the beginning of the reaction because ferrous acts as a catalyst for producing hydroxyl radical in ozonation. As ozone concentration increased, trihalomethane formation potential decreased. When 2 mg/L of ozone was injected, trihalomethane formation potential was shown to decrease and then increase again with the increase in ferrous concentration.

• Journal of the Korean Society for Railway
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• v.16 no.2
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• pp.117-121
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• 2013

Railway line segment deterioration can be affected by rail tracks, subgrades, bridges, tunnels, and line shapes. In this paper, an evaluation method is presented for the railway line segment deterioration using the analytic hierarchy process (AHP) and data envelopment analysis (DEA). The importance weights can be assessed systematically for component facilities from numerous experts using AHP. The importance weights provided by experts may differ according to each expert; however, the DEA enables the evaluation of railway line segment deterioration that reflects the variety of expert opinions using these importance weights.

• Proceedings of the Korean Society of Computer Information Conference
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• 2012.07a
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• pp.323-324
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• 2012

최근 스마트폰 환경에서 제공되는 수많은 서비스들은 일률적으로 소비자에게 단방향으로 제공되던 예전과 달리 사용자마다 개인화된 서비스 제공을 통해, 더욱 효율적으로 서비스를 제공하려는 시도들이 이루어지고 있다. 그 중에서 감정인식을 이용한 연구는 사용자에게 최적화된 개인화 서비스 제공을 위해 사용자의 감정을 인식하여 사용자가 느끼는 감정에 맞는 서비스를 제공함으로써 보다 몰입감을 느낄 수 있도록 하여 결과적으로 특정 서비스의 이용을 유도하도록 할 수 있다. 본 논문에서는 사용자 선호도와 컨텍스트 정보를 활용하여 사용자의 감정을 추출하고 이를 음성기반 감정인식과 융합하여 그 정확도를 높이고 실제서비스에서 활용할 수 있는 시스템 설계를 제안한다. 제안하는 시스템은 사용자 선호도와 컨텍스트 인식으로 감정을 판단했을 경우의 오류를 음성을 통한 감정인식으로 보완하며, 사용자가 감정인식 시스템을 활용하기 위한 비용을 최소화한다. 제안하는 시스템은 스마트폰에서 사용자 감정을 이용한 애플리케이션이나 추천서비스 등에서 활용이 가능하다.

• Nuclear Engineering and Technology
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• v.50 no.3
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• pp.327-339
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• 2018

This article presents a new global-local hybrid coarse-mesh finite difference (HCMFD) method for efficient parallel calculation of pin-by-pin heterogeneous core analysis. In the HCMFD method, the one-node coarse-mesh finite difference (CMFD) scheme is combined with a nodal expansion method (NEM)-based two-node CMFD method in a nonlinear way. In the global-local HCMFD algorithm, the global problem is a coarse-mesh eigenvalue problem, whereas the local problems are fixed source problems with boundary conditions of incoming partial current, and they can be solved in parallel. The global problem is formulated by one-node CMFD, in which two correction factors on an interface are introduced to preserve both the surface-average flux and the net current. Meanwhile, for accurate and efficient pin-wise core analysis, the local problem is solved by the conventional NEM-based two-node CMFD method. We investigated the numerical characteristics of the HCMFD method for a few benchmark problems and compared them with the conventional two-node NEM-based CMFD algorithm. In this study, the HCMFD algorithm was also parallelized with the OpenMP parallel interface, and its numerical performances were evaluated for several benchmarks.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.1
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• pp.68-76
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• 2015

This paper proposes the antenna selection scheme and power control algorithms of multiple nodes beamforming when the vehicles equipped with circular array antennas is moving and construct mobile mesh networks. The proposed antenna selection scheme chooses beamforming antenna elements considering antenna radiation gain and allows duplicated antenna selection for multiple adjacent nodes. The proposed power control algorithms maximize SIR for the duplicated antenna selection. The simulation demonstrates that the proposed antenna selection and power control achieve 2.5dB higher SIR gain than that of conventional methods when two nodes are apart from $15^{\circ}$.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.5
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• pp.475-481
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• 2019

The paradigm of convergence R&D is shifting from the convergence of technologies to the convergence of solutions to solve the complex problems of scientific and social development. On the other hand, it is prevalent that there is a lack of convergence in our research field. Although Korea has invested heavily in fusion research and development, Korea has mainly focused on the application and development of technology, so failed to plan convergence R&D in line with the new paradigm. Therefore, in this study, we searched for convergence R&D area that is being done to solve social problems, and tried to make use of data-driven objective methods. For this purpose, we used the investment information of global R&D projects that had no retrospective properties and derived the convergence R&D area related to coastal flooding.

• Journal of Korean Society of Water and Wastewater
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• v.33 no.3
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• pp.225-234
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• 2019

This study is focused on effects of factors that affect the formation of THMs during chlorination in drinking water treatment. During the chlorination, chlorine consumption is increased by increasing the initial chlorine dose, the pH and the total dissolved solid (TDS) concentration. Also THMs formation is increased up to $58.82{\mu}g/L$ and $55.54{\mu}g/L$ by increasing initial chlorine concentration and increasing pH. However, concentration of chloroform is decreased by increasing TDS concentration. This is caused the cation($Na^+$) of the total dissolved solids preferentially reacts with the functional groups of the organic material which influence the trihalomethane formation. But total trihalomethane formation is increased up to $127.46{\mu}g/L$ by $Br^-$ contained in the total dissolved solids. DOC reduction was not influenced by any of the factors.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.622-625
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• 2014

As Big data began to produce a variety of values, a database that allows for huge amount of data with varieties became to be needed. Therefore, for the purpose of overcoming the limitations of the complexity and capacity of the existing RDBMS, NoSQL databases were introduced. Among the different types of NoSQL databases, MongoDB is most commonly used and is offered as open sources. The B-Tree index, used in MongoDB, experiences a significant decrease in performance as the amount of data increases. The fractal tree index enables to enhance the performance of B-Tree substantially by improving B-Tree's insertion algorithm. In this paper, the performances of MongoDB when using B-Tree Index and when using Fractal Tree Index are compared.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.2
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• pp.201-208
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• 2019

Since the introduction of the open innovation at the beginning of the 2000s, various studies have been carried out on the convergence of technologies, such as the development of new technologies and the development of the business domain. while exploring the technologies necessary for the convergence of appropriate technologies in this research, we propose a discovery process of challengeable research areas by means of the integration of heterogeneous fields which are based on the strategic formulation of ICT and chemical safety industry. In this paper, we consequently propose the 103 detailed convergent technologies based on ICT, especially including artificial intelligent technology and smart big-data platform architecture, were derived from the research areas of the chemical safety field, We expect that research related to the safety field will be frustrated in the future.